Ice cliffs thousands of feet high criss-cross the surface of Dione, one of the large moons of Saturn, in this view from the Cassini spacecraft. The cliffs indicate that Dione has undergone recent tectonic activity that has cracked the crust. Recent Cassini observations suggest that an ocean of liquid water may lurk beneath the crust. [NASA/JPL/SSI]

The surface of Dione, one of the larger moons of Saturn, is a shell of ice pockmarked by craters. But there’s evidence that this icy crust once floated atop an ocean of liquid water — and still could do so today.

The Saturn-orbiting Cassini spacecraft has revealed several hints of a buried ocean. The ground below a long mountain chain is depressed by up to a third of a mile, for example. That suggests that when the mountains formed they were sitting atop a layer of material that was warmer than the icy crust — like liquid water.

Cassini has also sniffed a faint stream of particles flowing away from Dione. That could mean that a little bit of water is squirting out through old cracks in the crust — suggesting that there could still be a buried ocean today.

Two other moons of Saturn also appear to have buried oceans — Titan and Enceladus. Geysers of water and ice jet through cracks near the south pole of Enceladus. Dione could once have been as active as Enceladus is today. The combination of liquid water, the heat to keep it melted, and minerals in the water could have supplied the raw ingredients for life on Dione — adding a new target in the growing list of potential life-bearing worlds in the solar system.

Saturn stands close above our own Moon as night falls this evening. It looks like a bright golden star. The true star Spica is to their lower right. Saturn and the Moon slide down the sky later on, and set by about midnight.

Script by Damond Benningfield, Copyright 2013

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